The present disclosure relates to pleated air filters. More particularly, it relates to systems and methods for fabricating pleated filters on a mass-production basis that promote user-selected adjustment of the pleat spacing generated by the system.
Pleated filters are commonly used in air filtration and other applications. In general terms, pleated filters include a filter media formed into an accordion-like or pleated structure. The pleated filter media is secured within a frame (e.g., a paperboard frame). Various retention members (e.g., metal screens, scrims, strips, etc.) are often applied to the pleated filter media to provide additional support and maintain an integrity of the pleats in the presence of various operating pressures.
The surface area of the pleated filter media is a major factor in determining flow resistance (i.e., pressure drop) and loading capacity of the pleated filter. The surface area of the pleated filter media, in turn, is determined by the size or outer dimensions of the pleated filter, the depth of the pleats, and the pleat density. Because the external dimensions of pleated filters are often restricted to a particular end-use application, the pleat density (often times expressed in terms of number of pleats per inch) is the primary variable available to manufactures when fabricating different pleated filter formats. Higher performing pleated filters generally have more pleats per inch, and lower cost filters have lower pleats per inch. As a point of reference, pleat density is directly related to the spacing established between adjacent pleats (or “pleat spacing”).
Conventional automated methods of mass producing pleated filters include supplying a continuous web of the filter media to a pleating device. The pleating device folds the filter media at regular intervals, with the so-formed pleats being gathered in a relatively tight pack. The pleated filter media web is then processed through a pleat spacing device that adjusts and sets the pleats at a predetermined, uniform pleat spacing. For example, one conventional pleat spacing device conventionally employed in the automated fabrication of pleated filters is described in U.S. Pat. No. 4,976,677 (Siversson) and includes a helical screw conveyor in which the flight or pitch of the screw conveyor windings establishes the pleat spacing. Another well-known automated pleat spacer is described in U.S. Pat. No. 5,389,175 (Wenz) and U.S. Publication No. 2006/0283162 (Dent), and includes a conveyor having a plurality of spaced apart flites or cleats (e.g., a fixed pitch cleated conveyor). Individual ones of the flites or cleats carry or hold consecutive pleats during continuous movement of the conveyor, such that the resultant pleat spacing is dictated by the spacing between adjacent flites or cleats.
While automated pleat spacing devices are highly viable and well accepted, certain concerns may arise. With either helical screw or fixed pitch cleated conveyor pleat spacing devices, the pleat spacing imparted by the device is fixed and is not easily adjusted. For example, the pitch defined by the helical windings of the screw conveyor pleat spacing device is fixed. Thus, when a pleated filter having a pleat spacing differing from that provided by the currently in-use helical screw is desired, the current screw must be replaced with a different helical screw having the desired pitch. Similarly, the flites or cleats provided with a fixed pitch cleated conveyor are robustly mounted to the conveyor. In order to adjust the pleat spacing established by the cleated conveyor, production must be stopped, and the multiple flites or cleats manually adjusted to establish a new spacing.
In light of the above, a need exists for improved systems and methods for fabricating pleated filters that provide simplified adjustment of a pleat spacing effectuated by the system and method.